Selenium rectifier



Dec. 14, 1954 1, GQLDMAN ETAL 2,697,188

SELEINIUM RECTIFIER Filed March 16, 1949 2 Sheeis-Sheet 1 K3455 PLA7\ SUPPORT STRIP nn- L :3

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Robe/4'5 Goldman 'vm m Irwin Dec. 14, 1954 GQLDMAN ETAL SELENIUM RECTIFIER Filed March 16, 1949 \SIIPPORT STRIP SUPPORT STRIP B/lRR/El? ELENIUM PLASTIC TRODE COUNTER-LEC 505E PLATE 2,697,188 Patented Dec. 14, 1954 2,697,188 SELENIUM RECTIFIER Erwin Goldman, Laurelton, and William Roberts, Flushing, N. Y., assiguors to Sylvania.Electric Products,

c., a corporation of Massachusetts Application March 16,1949, Serial No. 81,774 3 Claims. (Cl. 317-234) This invention relates to dry or contact rectifiers and the method of making them; more particularly it relates to rectifiers of the selenium type.

The selenium rectifiers of the prior art have for the most part consisted of a base plate whichis continuous except for a central hole. This selenium to a crystalline allotrope which material is coated with a counterelectrode and finally electroformed to develop proper electrical characteristics; In theory the nickel or bismuth coating is believed to proor bismuth is principally mechanical and unless the continuous substrate has blasting, etching or other means roughen the surface by either mechanical or chemical means. Following this step, it is necessary to apply a thin film of nickel or bismuth on the roughened surface prising. the rectifier, namely the base plate, selenium; a forming material, spacingv material, counterelectrode and protective lacquer.

he accompanying drawings which illustrate pre- Fig. 7 is a section through line 7-7 of Fig. 6.

Fig. 8 is a side view partly in section of a modified structure of. the rectifier of this invention.

Fig. 9 is a side view of another modified'structure of this invention.

Fig. 10 is a plan view of another modified structure of this invention. 7

Fig. 11 is a plan. view of a modified version of the structure of Fig. 10.

Inv the preferred practice of this invention, a strip of non-electrically conductingv material such as plastic or ceramic is first roughened as by sand blasting to provide a clean, rough surface exhibiting secure adhesion to any metal deposited thereon. When the strip of non-electrically conducting material has been properly roughened, it is ready for the deposition of the first or base plate material as indicated in Figs. l-7 of the drawings. This film of base plate material may be deposited upon the strip in many ways. However in accordance with embodiment of this invention, the base plate material can be deposited'upon the'd'esired areas of strip material bya spray operation utilizing a proper masking device.

en makinga rectifier of the design illustrated in Figs. 1 through 7 of the drawings, this masking device is so in any lgnown manner including the'preferred manner of spraying;

can besprayed onto all ,of'the exposed metal surfaces'as indicated in Fig. 3. Following the ap lication of the Subsequent to this and bv utilizing still another maskmg device base plate material of the selenium surfaces Whichhave A distinctive feature operation which is conducted with the use of a masking device similar to that used in the preceding step with the exception that now those selenium layers which have beneain them counterelectrode material are now sprayed with material of base plate composition. This masking arrangement also has the distinctive feature of allowing an over-spray of the base plate material onto the plastic spacing composition to permit the making of adequate electrical contact at the juncture between the sprayed counterelectrode and the sprayed base plate materials. A completed six plate strip is shown in Figs. 6 and 7. As a final step, lacquer may be sprayed over the whole unit without the use of a masking device in order to add corrosion resistance to the assembly. However, prior to the lacquering, it is preferable to anneal the selenium to form the metallic conductive modification. This step however, may be performed immediately after the application of the selenium and prior to further processing. Prior to the lacquering it is also preferable to electroform the completed unit. The electro-forming operation being carried out on the strip as a unit, or on the individual plates or groups of plates as desired.

There are many advantages which can be claimed for the strip rectifiers manufactured in accordance with the preceding description. For example, it is very simple to manufacture. It requires no assembly. The process lends itself to continuous processing of the strip and subsequent cutting into units of the desired number of plates. The number of plates per unit being determined by the desired output per strip. Furthermore, it permits flexibility of design in that by other changes in the masking devices parallel, series or bridge type rectifier strips may be produced. Furthermore, the strip type rectifier design will permit of greater heat dissipation and thereby allow the ectifier to be operated at a higher output than is possible with the stacked rectifiers.

Another advantage of this type of rectifier design is that it leads to over-all manufacturing economies in that fewer parts are required for assembly. The equipment required for manufacture is simplified and standardized and the process can be completely automatic requiring the attention of only supervisory and maintenance personnel.

In considering the process here and above described, it should of course be understood that the base plate material may be made of any material which has a high work function. Materials of this type which are known and have been used in the prior art include bismuth, nickel, cadmium, cobalt, manganese, iron, chromium and alloys of bismuth, cadmium, lead and tin. The counterelectrode material should be one which has a lower work function than the base metal chosen. For this purpose, use is frequently made of cadmium, tin and alloys of cadmium, tin, bismuth and lead. The bismuth only being useable at those times when the base metal is not bismuth.

In those cases in which the spray technique is used as described for the preferred embodiment of the invention, the base plate metal and counterelectrode metal should preferably be sprayable at temperatures sufficiently low to prevent injury to the selenium when sprayed thereon. Of course when methods other than spraying are are used this temperature characteristic is not of as critical importance.

As has been implied, heretof re, the selenium may of course, be ap lied in many different ways. as for example. by spraying or pressing. However, if the spraying techni ue is used, the conditions of spraying, e. g., distance of un from work, temper ture, etc.. will depend upon the type of spray mechanism used (powder, wire or molten metal). he lower the temperature is kept. the more easy it will be to avoid vaporization of the selenium.

The plastic coating over the counterelectrode may also serve another function in that it can act as an insulat r to prevent shorts between the countere ectrode material and the base l e material if any cracks or fissures appear in the selenium.

It is of course. understandable that other modificatinns can be made without departing from the spirit of this invention. For example, a sprayed strip rectifier of the type disclosed may also be made on one side of a non-electrical conducting strip so that the unspraved or uncoated side may be fastened directly, to an electrically conducting surface such as a metal radio chassis.

4 A structure of this type is shown in Fig. 8 of the drawing. The plastic supporting strip there shown is coated on one side with successive coatings of base plate material,

, counterelectrode material, barrier layer forming material and insulating material. Furthermore it should be understood that the sprayed rectifier can be made on a supporting strip of a plastic or the like which is shaped other than fiat for improved structural strength. For example, it might be desirable to make use ofa corrugated supporting strip as shown in Fig. 9. This, besides giving improved structural strength would also give a greater surface area for rectification.

Fig. 10 shows still another version or modification of this design. In this case, the base metal or base plate material is sprayed directly onto the supporting material in all cases with the selenium coating lying between it and a counterelectrode positioned directly there-above so that in each unit the counterelectrode is positioned farthest away from the supporting plate and contact being made between it and the base plate of the next unit.

Fig. 11 shows another modification of the strip rectifier shown in Fig. 10. It differs from that shown in Fig. 10 only in providing a separate overspray of insulating material to permit the counterelectrode to extend beyond the edge of the individual rectifier element and thus be in position for contact with the base metal of the preceding rectifier element.

In working with strip rectifiers of this type it has further been found that the density of the selenium coating has a decided effect on the results obtained. For example, it has been found that when a sprayed selenium surface is further processed by pressing the surface with a hot roller or platen for as little as ten to twenty seconds and thereby densifying it, the average value of forward current can be increased by as much as a multiple of 2. It is of course, obvious that rectifiers of the construction described herein readily lend themselves to use in the so-called printed circuits.

As can readily be seen from the above description,

the rectifier of this invention readily lends itself to the manufacture of an all-sprayed strip rectifier and thus can readily be made by a continuous process. When using a continuous process it is naturally advantageous to start with a flexible supporting strip material. Fortunately, the process is conveniently applicable to the use of a continuous strip of flexible material such as fiber glass which may have for its first step in the process an immersion in a B stage phenolic resin. Polymerization of the resin and consequent stiffening of the fiber glass strip can be made to take place at some subsequent stage in the manufacture of the rectifier. From the above, it is therefore readily apparent that the rectifiers of this invention can be made with either a rigid or a flexible strip material in its early processing stages. In some instances, fiexible material may be preferred particularly if the process is to be a truly continuous one.

' Whilethe above description and the drawings submitted herewith disclose preferred and practical embodiments of the rectifiers of this invention, it will be understood by those skilled in the art that the specific details of construction and arrangement of parts as shown and described are by way of illustration and are not to be construed as limiting the scope of the invention.

What is claimed is:

l. A current rectifier comprising a plurality of rectifying units superimposed on the surface of a non-conductive material having a corrugated cross section, each of said rectifying units comprising a film of base plate material immediately adjacent said non-conductive material, selenium films adjacent to said base plate material and superimposed thereon, and a counterelectrode adjacent each selenium film and superimposed thereon.

2. A current rectifier comprising-a plurality of inversely positioned rectifyingunits superimposed on both surfaces of a non-conductive material, said rectifying units comprising superimposed sprayed materials of base plate material, selenium and counterelectrode.

3. A current rectifier comprising a plurality of inversely positioned rectifying units in electrical contact with oneanother superimposed on both surfaces of a non-conductive material, said rectifying units comprising superimposed sprayed films of rectifying elements,

said electrical contact bein non-conductive material.

Number Name Rupp Veszi et a1.

g made over the edge of said Date July 25, 1933 Oct. 7, 1947 Number 6 Name Date Escoffery et a1. Dec. 28, 1948 Bugel et a1. Oct. 25, 1949 Searle Feb. 28, 1950 Kotterman Feb. 28, 1950 Kotterman June 6, 1950 Teal June 12, 1951 Hyde May 20, 1952 

1. A CURRENT RECTIFIER COMPRISING A PLURALITY OF RECTIFYING UNITS SUPERIMPOSED ON THE SURFACE OF A NON-CONDUCTIVE MATERIAL HAVING A CORRUGATED CROSS SECTION, EACH OF SAID RECTIFYING UNITS COMPRISING A FILM OF BASE PLATE MATERIAL IMMEDIATELY ADJACENT SAID NON-CONDUCTIVE MATERIAL, SELENIUM FILMS ADJACENT TO SAID BASE PLATE MATERIAL AND SUPERIMPOSED THEREON, AND A COUNTERELECTRODE ADJACENT EACH SELENIUM FILM AND SUPERIMPOSED THEREON. 